This disclosure relates to printing methods, systems and apparatus to compensate for distortion caused by fusing toner applied to a media substrate. According to one exemplary method, image data is processed according to media characterization data for a measured fuser temperature to compensate for media substrate shrinkage due to fusing a printed image on the media substrate.
Electrophotographic marking is a well-known and commonly used method of copying or printing documents. In general, electrophotographic marking employs a charge-retentive, photosensitive surface, known as a photoreceptor, that is initially charged uniformly. In an exposure step, a light image representation of a desired output focused on the photoreceptor discharges specific areas of the surface to create a latent image. In a development step, toner particles are applied to the latent image, forming a toner or developed image. This developed image on the photoreceptor is then transferred to a print sheet on which the desired print or copy is fixed.
The electrophotographic marking process outlined above can be used to produce color as well as black and white (monochrome) images. Generally, color images are produced by repeating the electrophotographic marking process to print two or more different image layers or color image separations in superimposed registration on a single print sheet. This process may be accomplished by using a single exposure device, e.g. a raster output scanner (ROS), where each subsequent image layer is formed on a subsequent pass of the photoreceptor (multiple pass) or by employing multiple exposure devices, each writing a different image layers, during a single revolution of the photoreceptor (single pass). While multiple pass systems require less hardware and are generally easier to implement than single pass systems, single pass systems provide much greater print speeds.
In generating color images, the ability to achieve precise registration of the image layers is necessary to obtain printed image structures that are free of undesirable color fringes and other registration errors. In addition, when generating duplex printed documents, registration of images on a document is important where individual sheets or pages are bound. For example, in duplex printing of sheets or pages intended for binding, in order to provide a quality print job which is competitive in the market place, it is necessary that the print on both sides of the pages be registered or positioned on the page such that there is no noticeable variation to the reader of the print on the page from the first to the second side. It has been found that variations of 2 mm or less in the image registration from Side 1 to Side 2 of a sheet or page are quite noticeable to the eye of the reader and give the impression of a poor quality print job. Accordingly, it has been found necessary to maintain very tight control of the image magnification or registration in duplex printing from Side 1 to Side 2, or front to back, of the printed media sheet.
Maintaining the aforesaid tight control of print magnification from Side 1 to Side 2 in a duplex printing job on an electrostatic photocopier has proven to be difficult and costly in such machines set up for high speed duplex printing. This has been found to be the case irrespective of whether the digital image is transferred directly to the electrostatic printing machine such as from a computer or is generated from a printed sheet inputted for copying and reproduction. The complexity of the processes within the electrostatic print engine including the transport of the paper through the sheet path and heat fusing in the print engine has introduced error in the print magnification and registration from Side 1 to Side 2 on a printed sheet.
One cause of misregistration of printed images on a xerographic printer is that paper media gets distorted as it passes through a fuser. It is desirable to have methods, apparatus and systems to compensate for distortions caused by fusing.